Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector X4 from the PCB
Measurement:
Test 1:
Measure the resistance between pin 3 and pin 4 on connector X4.
Expect approximately 3.1 kohms.
Test 2:
Measure the resistance between pin 4 and the earth at the incoming mains supply.
Expect a resistance greater than 1 Mohm.
Are the resistances measured as expected?
Measure the resistance between pin 3 and pin 4 on connector X4.
Expect approximately 3.1 kohms.
Test 2:
Measure the resistance between pin 4 and the earth at the incoming mains supply.
Expect a resistance greater than 1 Mohm.
Are the resistances measured as expected?
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Isolate as per TOPs P4
and refit as necessary